During operation of typical dialysis machines performing hemodialysis, blood is passed through a dialysis chamber on one side of a dialysis membrane and a dialysate is passed on the other side of the dialysis membrane. In addition to diffusion of solutes across the dialysis membrane, a difference in pressure between the blood-side and the dialysate-side of the dialysis membrane drives the bulk movement of water from higher pressure to lower pressure. The pressure generated on a particular side of the dialysis membrane depends on several factors including flow rate, viscosity of the fluid, geometry of the dialyzer and physiological condition of the patient. The diffusion of impurities from the blood, across the dialysis membrane and into the dialysate is thermodynamically driven by the concentration gradient difference between the concentration of impurities in the blood and the concentration of those species in the dialysate. In most dialysis systems, large volumes of water are required to form the dialysate thereby requiring patients to regularly travel to a dialysis center to receive treatment for a chronic disease. In effect, dialysis patients are tethered to their dialysis center.
Moreover, dialysis treatments performed at dialysis centers are administered intermittently and fail to replicate the continuous waste removal aspect of a natural and functioning kidney. Once a dialysis session is completed, fluid and other substances such as sodium and potassium salts immediately begin to accumulate in the tissues of the patient. Notwithstanding the benefits of dialysis, statistics indicate that three out of five dialysis patients die within five years of commencing treatment. Studies have shown that increasing the frequency and duration of dialysis sessions can improve the survivability of dialysis patients. Increasing the frequency and duration of dialysis sessions more closely resembles continuous kidney function. However, the requirement for patients to travel to the dialysis centers and the costs associated with the hemodialysis procedure itself pose an upper limit on the frequency of dialysis procedures.
Known attempts to make portable dialysis systems usually rely upon the regeneration of spent dialysate (i.e. dialysate having urea and/or other impurities therein) to form refreshed dialysate that can be reused to perform dialysis. However, large quantities of water are required to reuse spent dialysate thereby limiting portability. Accumulated waste products and impurities must be removed from the spent dialysate, and the composition and pH of the regenerated dialysate must be regulated for physiological compatibility. Generally, regeneration of spent dialysate requires use of a sorbent cartridge through which spent dialysate is recirculated and regenerated. However, regenerated dialysate produced by known systems is subject to variations in pH and sodium concentrations non-conducive to physiological norms. Further, zirconium-based exchange materials used in many known sorbent systems are expensive and can release ions into the dialysate that affect conductivity and/or the pH of the dialysate, which necessitates the addition of further reagents to the dialysate to maintain the composition of the dialysate.
Hence, there is a need for a convenient dialysis system that can regenerate dialysate in a cost-effective manner. The system should remove impurities from spent dialysate solution. The system should have a weight and volume that is sufficiently light and small to be practicably carried by the patient while ambulatory. There is a need for a system that would allow a patient to travel wherein the system is no larger than about the size of luggage suitable for storage in an overhead bin of an airplane. Further, to facilitate regular usage, the system should be conducive to operation by a patient without the assistance of a medical professional.
There is also a need for a system that can be quickly set up in a new location without requiring specific sources of water or new water lines or pipes. The system must be patient-friendly and capable of operating on a small volume of dialysate and suitable for daily use, continuous use, short-term use, or use in a home-setting. There is also a need for a modular system that can provide any one or combination of hemodialysis, hemofiltration, hemodiafiltration and peritoneal dialysis.